[RESOLVED] starting on writing a class - i have a question

steamPunk

I've been using other people's classes recently but now i feel it's time to write my own

i was wondering, though, if a function outside a class can be used within a class - or would i need to make that external function into a class itself ?

the reason i'm asking is that I have a couple of functions that would be used by several classes

thanks

bpat1434

You can use a function outside a class just like any other function:

function myFunction()
{
    return 5;
}

class demoClass
{
    function whatNumber()
    {
        echo myFunction();
    }

function add($num)
{
    echo $this->_add($num, myFunction());
}

private function _add($num, $num2)
{
    return $num + $num2;
}
}

Notice how you can use internal functions using the $this-> keyword, and external functions just like normal?

steamPunk

yes - that explains it perfectly

thanks !

NogDog

You can do it, but it goes against one of the main benefits of OOP: keeping your code as modular and loosely coupled as reasonably possible. By calling a user-defined function within your class, you now create a dependency between that class and the separate function definition, with nothing in the class's template indicating there is such a dependency.

It might make more sense for that separate function to be either within its own class or - perhaps more likely - grouped together with related functions as methods within some class of their own. Then you would pass that class to the other class, therefore making it explicit in that second class's interface that it depends on that other class.

class Utilities
{
   function myFunction()
   {
      echo "Hello, World.";
   }
}

class DemoClass
{
   protected $utils;
   public function __construct(Utilities $util)
   {
      $this->utils = $utils;
   }
   public example()
   {
      $this->utils->myFunction();
   }
}

$test = new DemoClass(new Utilities());
$test->example();  // should output "Hello, World."

steamPunk

NogDog;10878391 wrote:
By calling a user-defined function within your class, you now create a dependency between that class and the separate function definition, with nothing in the class's template indicating there is such a dependency.

I see your point : if i use the class on another site i would probably forget to copy the function across as well, and spend hours trying to figure out why it doesn't work

however, i don't really understand what this bit does :

   protected $utils;
   public function __construct(Utilities $util)
   {
      $this->utils = $utils;
   }

as far as i can tell, when an instance of DemoClass is created an instance of Utilities is created too as a kind of 'argument' - is that what tells the _construct(Utilities $util) function to run ?

bpat1434

__construct() is a "magic" function in that it will run when the class is instantiated. So by saying:

$object = new DemoClass(new Utilities());

the demo object now has a way to "talk" to the utilities class and utilize its functions.

In a way it's the crude way of doing inheritance or extension.

steamPunk

okayyyy

so it's declared as "protected $utils;" to keep it safe as a reference to the other class

yes I think i get the general idea

now i need to implement this .....

thanks for your help 🙂

NogDog

You'll have to decide for your purposes whether it makes sense that it be public, protected, or private. I tend to default to protected when it's not immediately obvious that it should be public, as it keeps access to that attribute controlled but inheritable; then I change it to public or private if/when I see a need for that.

bpat1434

I'm the other way around. I tend to be private at first, then only open up those items that need to be opened up. Start with the highest security, then allow access to only those that need it. Less chance of seeing something going wrong 😉